Multi-protocol i/o interconnect flow control

ABSTRACT

Described are embodiments of methods, apparatuses, and systems for multi-protocol tunneling across a multi-protocol I/O interconnect of computer apparatus. A method for managing flow across the multi-protocol I/O interconnect may include providing, by a first port of a switching fabric of a multi-protocol interconnect to a second port of the switching fabric, a first credit grant packet and a second credit grant packet as indications of unoccupied space of a buffer associated with a path between the first port and a second port, and simultaneously routing a first data packet of a first protocol and a second data packet of a second protocol, different from the first protocol, on the path from the second port to the first port based at least in part on receipt by the second port of the first and second credit grant packets. Other embodiments may be described and claimed.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to multi-protocol tunneling across a multi-protocol I/O interconnect of a computer apparatus.

BACKGROUND

Conventional computer platform architectures include a variety of host controllers to implement a number of different types of I/O between computer platforms and peripheral devices that are connected to the platforms, and these computer platforms generally include protocol-specific connection interfaces that connect to the peripheral devices via protocol-specific plugs and cables. For example, a computer may include one or more of a USB-specific controller that connects to a peripheral device via a USB-specific connection interface, a display-specific controller (e.g., DisplayPort) that connects to a peripheral device via a display-specific connection interface, a PCI Express®-controller that connects to a peripheral device via a PCI Express®-specific connection interface, and so on.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will be described by way of example embodiments, but not limitations, illustrated in the accompanying drawings in which like references denote similar elements, and in which:

FIG. 1 describes a computer apparatus including a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure.

FIG. 2 describes a computer system including a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure.

FIG. 3 describes a switching fabric of a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure.

FIG. 4 describes a protocol stack for a multi-protocol interconnect architecture of an I/O complex, in accordance with various embodiments of the present disclosure.

FIG. 5 describes an implementation of a protocol stack for a multi-protocol interconnect architecture of an I/O complex, in accordance with various embodiments of the present disclosure.

FIG. 6A describes a physical topology of a domain of switches, and FIG. 6B describes an embodiment of a spanning tree for managing the domain of FIG. 6A, in accordance with various embodiments of the present disclosure.

FIG. 7 describes a spanning tree in a domain, in accordance with various embodiments of the present disclosure.

FIG. 8 describes a format of a route string for routing configuration packets in a domain, in accordance with various embodiments of the present disclosure.

FIG. 9 describes a format of a topology ID configuration register, in accordance with various embodiments of the present disclosure.

FIG. 10 describes connections that may be established between multiple domains, in accordance with various embodiments of the present disclosure.

FIG. 11 describes a multi-protocol tunneling I/O complex and interconnect, in accordance with various embodiments of the present disclosure.

FIG. 12 describes a multi-protocol tunneling I/O complex and interconnect, in accordance with various embodiments of the present disclosure.

FIG. 13 describes a device (e.g., a peripheral device) including a multi-protocol tunneling I/O interconnect connected with a multi-protocol tunneling I/O interconnect, both in accordance with various embodiments of the present disclosure.

FIG. 14 describes an architecture for mapping a DisplayPort stream over a multi-protocol switching fabric, in accordance with various embodiments of the present disclosure.

FIG. 15 describes a structure of a scan line and the packetization performed by the DisplayPort IN adapter, in accordance with various embodiments of the present disclosure.

FIG. 16 describes a link initialization sequence of DisplayPort link training, in accordance with various embodiments of the present disclosure.

FIG. 17 describes an architecture for mapping an HDMI stream over a multi-protocol switching fabric, in accordance with various embodiments of the present disclosure.

FIG. 18 describes a video island packet format, in accordance with various embodiments of the present disclosure.

FIG. 19 describes a data/control island packet format, in accordance with various embodiments of the present disclosure.

FIG. 20 describes an overall architecture of a credit-based flow control, in accordance with various embodiments of the present disclosure.

FIG. 21 describes flow control buffer space at a receiver, in accordance with various embodiments of the present disclosure.

FIG. 22 describes various flow control schemes assuming eight flow controlled paths P1-P8, in accordance with various embodiments of the present disclosure.

FIG. 23 describes tracking of information at a transmitter and receiver, in accordance with various embodiments of the present disclosure.

FIG. 24 describes handling of a path credit sync packet at a transmitter and receiver, in accordance with various embodiments of the present disclosure.

FIG. 25 describes handling of a link credit sync packet at a transmitter and receiver, in accordance with various embodiments of the present disclosure.

FIG. 26 is a flow diagram of a method for configuring a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure.

FIG. 27 is a flow diagram of a method for operating a computer apparatus including a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure.

FIG. 28 describes an article of manufacture having programming instructions configured to cause an apparatus to practice some or all aspects of multi-protocol tunneling (of the methods of FIGS. 23-27, for example), in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that alternate embodiments may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that alternate embodiments may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments.

Further, various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the illustrative embodiments; however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. Moreover, methods within the scope of this disclosure may include more or fewer steps than those described.

The phrase “in some embodiments” is used repeatedly. The phrase generally does not refer to the same embodiments; however, it may. The terms “comprising,” “having,” and “including” are synonymous, unless the context dictates otherwise. The phrase “A and/or B” means (A), (B), or (A and B). The phrase “A/B” means (A), (B), or (A and B), similar to the phrase “A and/or B”. The phrase “at least one of A, B and C” means (A), (B), (C), (A and B), (A and C), (B and C) or (A, B and C). The phrase “(A) B” means (B) or (A and B), that is, A is optional.

FIG. 1 describes a computer apparatus 100 including a multi-protocol tunneling I/O interconnect 108 in accordance with various embodiments. In many embodiments, the computer apparatus 100 may include one or more processors 102. In different embodiments, the one or more processors 102 may include one core or multiple cores. In some embodiments, the apparatus 100 may be a multiprocessor system (not shown) where each of the processors has one core or multiple cores.

As shown in FIG. 1, the one or more processors 102 may be operatively coupled to system memory 104 through one or more links (e.g., interconnects, buses, etc). System memory 104 may be capable of storing information that the one or more processors 100 utilize to operate and execute programs and operating systems. In different embodiments, system memory 104 may be any usable type of readable and writeable memory such as a form of dynamic random access memory (DRAM).

In previously implemented computer apparatuses, an I/O link connecting a peripheral device to a computer system is protocol-specific with a protocol-specific connector port that allows a compatible peripheral device to be attached to the protocol-specific connector port (i.e., a USB keyboard device would be plugged into a USB port, a router device would be plugged into a LAN/Ethernet port, etc.) with a protocol-specific cable. Any single connector port would be limited to peripheral devices with a compatible plug and compatible protocol. Once a compatible peripheral device is plugged into the connector port, a communication link would be established between the peripheral device and a protocol-specific controller.

In the computer apparatus as described in the embodiment shown in FIG. 1, the one or more processors 102 may be operatively coupled to an I/O complex 106, which may house one or more multi-protocol I/O interconnects 108 configured to control one or more I/O links that allow the one or more processors 102 to communicate with one or more I/O peripheral devices 110. For providing the multi-protocol capability, at least in part, the I/O interconnect 108 may include a multi-protocol switching fabric 114 configured to carry multiple I/O protocols. In various embodiments, the multi-protocol switching fabric 114 may comprise a plurality of cross-bar switches. Examples of I/O peripheral devices 110 may include a display device, a keyboard device, an expansion port, a desktop or mobile computer system, or a router, among other devices.

A non-protocol-specific connector port 112 may be configured to couple the I/O interconnect 108 with a connector port (not shown) of the device 110, allowing multiple device types to attach to the computer system 100 through a single physical connector port 112. Moreover, the I/O link between the device 110 and the I/O complex 106 may be configured to carry multiple I/O protocols (e.g., PCI Express®, USB, DisplayPort, HDMI®, etc.) simultaneously. In various embodiments, the connector port 112 may be capable of providing the full bandwidth of the link in both directions with no sharing of bandwidth between ports or between upstream and downstream directions. In various embodiments, the connection between the I/O interconnect 108 and the device 110 may support electrical connections, optical connections, or both.

The apparatus 100 may be a stand-alone device or may be incorporated into various systems including, but not limited to, various computing and/or consumer electronic devices/appliances, such as desktop computing device, a mobile computing device (e.g., a laptop computing device, a handheld computing device, a tablet, a netbook, etc.), mobile phones, smart phones, personal digital assistants, servers, workstations, set-top boxes, digital reorders, game consoles, digital media players, and digital cameras. A block diagram of an example system 200 is illustrated in FIG. 2. The system 200 may comprise one or more processor(s) 202, system memory 204, and an I/O complex 206, all operatively coupled by a bus 115. The I/O complex 206 may include one or more multi-protocol I/O interconnects 208, each of which include a switching fabric 214 and control one or more I/O links that allow the one or more processors 202 to communicate with one or more I/O peripheral devices 210. In various embodiments, the system 200 may have more or fewer components, and/or different architectures.

The system 200 may include communications interface(s) 217 operatively coupled to the bus 215 to provide an interface for system 200 to communicate over one or more networks and/or with any other suitable device. The communications interface(s) 217 may include any suitable hardware and/or firmware. The communications interface(s) 217 for one embodiment may include, for example, a network adapter, a wireless network adapter, a telephone modem, and/or a wireless modem. For wireless communications, the communications interface(s) 217 for one embodiment may include a wireless network interface controller 219 having one or more antennae 221 to establish and maintain a wireless communication link with one or more components of a wireless network. The system 200 may wirelessly communicate with the one or more components of the wireless network in accordance with any of one or more wireless network standards and/or protocols.

The system 100 may include a display device 223, such as, for example, a cathode ray tube (CRT), liquid crystal display (LCD), light emitting diode (LED), or other suitable display device, operatively coupled to the bus 215 for displaying information. In various embodiments, the display device 223 may be a peripheral device interconnected with the system 200. In various ones of these embodiments, such a peripheral display device may be interconnected with the I/O complex 206 by way of the multi-protocol port 212.

As described herein, for providing an I/O interconnect capable of carrying multiple I/O protocols, one or more of the various I/O interconnects described herein may include, among other things, a multi-protocol switching fabric 314 comprising a plurality of cross-bar switches, as shown in FIG. 3. The multi-protocol switching fabric 314 may be similar to other multi-protocol switching fabrics described herein. In general, the switches 316 a, 316 b are devices comprising multiple ports 320 s, 320 b, 322 a with the ability to route a packet from any input port to any output port. In various embodiments, the switches 316 a, 316 b may comprise any number of ports 320 s, 320 b, 322 a, with each additionally including an internal control port 326 a, 326 b. The switches 316 a, 316 b may each optionally include a time management unit 330 a, 330 b for use in distributing and synchronizing time throughout the multi-protocol switching fabric 314, as described more fully herein.

Switch 316 a may represent a first type of switch including null ports 320 a configured to connect to a single optical or electrical link, while adapter ports 322 a may be configured to connect to one or more mapped I/O protocol links. The adapter ports 322 a may be used to connect mapped I/O protocol entities to the multi-protocol switching fabric 314. As used herein, the term “adapter” may be used to refer to the protocol adaptation function that may be built into the switch port to encapsulate the mapped I/O protocol packets into I/O packets that flow over the multi-protocol switching fabric 314.

Switch 316 b may represent a second type of switch including only null ports 320 b (like null ports 320 a) configured to connect to a single optical or electrical link.

Although the switches 316 a, 316 b depicted in FIG. 3 each include four adapter ports 322 a and four null ports 320 a, 320 b, the actual number of ports 320 a, 320 b, 322 a may be fewer or more than that shown. In order to provide connectivity between switches 316 a, 316 b, a switch implementation generally minimally includes either at least one null port and at least one adapter port, or at least two null ports.

In various embodiments, the multi-protocol switching fabric 314 may comprise one or more of the first type of switches 316 a and one or more of the second type of switches 316 b.

For implementing various multi-protocol tunneling between adapter ports of a switching fabric within the scope of the present disclosure, a connection manager (not illustrated) may be provided. The connection manager may be implemented in software, firmware, as logic within an I/O complex, as part of a system BIOS, or within an operating system running on a computer apparatus or system in which the I/O complex is included.

An example protocol stack for the multi-protocol interconnect architecture of an I/O complex is shown in FIG. 4. The electrical and optical sublayers, the logical sublayer, the transport layer, and the frame layer may define the base multi-protocol interconnect architecture of the I/O complex, in which the physical layer comprises the electrical, optical, and logical sublayers. The mapped protocol layers may describe the mapping of the specific I/O protocols onto the multi-protocol interconnect architecture.

In various embodiments, and with reference to FIG. 3 and FIG. 4, the transport layer may be implemented by all ports 320 a, 320 b, 322 a of the switches 316 a, 316 b of the multi-protocol switching fabric 314, the physical layer may be implemented by all null ports 320 a, 320 b, and the adapter ports 322 a may implement a single mapped protocol layer or the frame layer.

An example implementation of the protocol layering is shown in FIG. 5. In the example shown, two protocols are implemented using switches 516 a, 516 b, 516 c, 516 d. Each of the switches 516 a, 516 b, 516 c, 516 d include control ports 526 a, 526 b, 526 c, 526 d, and time management units 530 a, 530 b, 530 c, 530 d.

As shown, the adapter ports 522 a 1, 522 c implement a first protocol layer (or frame layer) “protocol 1,” and adapter ports 522 a 2, 522 d implement a second protocol layer (or frame layer) “protocol 2.” All ports implement the transport layer, while the physical layer is implemented by all null ports 520 a, 520 b, 520 c, 520 d.

As such, a link (e.g., link 532) between ports of switches may effectively be shared by multiple paths traversing the fabric between adapter ports of the multi-protocol switching fabric. In various embodiments, the multi-protocol interconnect architecture may be connection-oriented such that a path is configured end-to-end before data transfer takes place. The path may traverse one or more links through the multi-protocol switching fabric, and each hop, the path may be assigned a locally unique identifier that may be carried in the header of all the packets that are associated with the path. In various embodiments, packets belonging to the path may not be reordered within the multi-protocol switching fabric. Buffer allocation (flow control) and Quality of Service may be implemented on a per-path basis. As such, a path may provide virtual-wire semantics for a mapped I/O protocol across the multi-protocol switching fabric.

In various embodiments, the physical topology of a collection of switches (a domain) may be an arbitrarily interconnected graph. FIG. 6A shows an example of a physical topology of a domain of switches 1-6. It should be noted that a domain is a management concept rather than an operational one. In various embodiments, a connection manager, as described earlier, may configure the domains of a switching fabric. For further management purposes, a multi-protocol apparatus may be configured to create a spanning tree (by way of the connection manager, for example). FIG. 6B shows an example spanning tree created for managing the domain of FIG. 6A in which the switch 1 at the top of the spanning tree may be referred to as the root switch. It is noted that a spanning tree may include any suitable number of levels. In various embodiments, the maximum number of levels of the spanning tree may be seven.

FIG. 7 shows an example of a spanning tree in a domain. Also shown are example assignments of unique topology IDs to each of the switches in the domain. For example, switch J has a topology ID of 0,4,1,1,2,1,8. In various embodiments, unique topology IDs may be assigned to every switch of a domain and each topology ID may represent the position of the switch within the spanning tree of the domain. In various embodiments, the assignment of the topology IDs may be done by the connection manager during initialization in which the domains may be created by enumerating the switches that are reachable and the topology IDs may be assigned for each switch.

As shown in FIG. 7, the domain includes seven levels (levels 0-6), and the topology IDs of each of the switches are sequences of seven port numbers representing the egress ports at each level of the tree on the path, from the root switch to itself. The topology ID of a switch at a depth of X (where X is from 0 to 6 in this example) may contain a non-zero port number for levels 0 to X−1. The port number at depth X may be 0 denoting the control port of the switch at depth X. The port numbers from depth X+1 to 6 may be treated as “don't care” and may be set at 0. Thus, in the example shown, the control port at the root switch has a topology ID of 0,0,0,0,0,0.

In various embodiments, the routing of configuration packets flowing downstream (in relation to the spanning tree) may be based on the topology ID of the target switch. The configuration packets may be routed in the transport layer packet header. In various embodiments, configuration packets flowing upstream may not use the topology ID and may simply be forwarded over the upstream port of each switch. Typically, every configuration packet carries a route string included in its payload. An example format of the route string is shown in FIG. 8. As shown, the route string may essentially be the topology ID of the switch to which the configuration request is sent or from which the configuration response originates. The MSB bit (CM bit) of the route string may be set to 0 when the configuration message is flowing downstream (from the connection manager to the switch) and set to 1 if the message is flowing in the upstream direction.

In various embodiments, each switch may be configured with its topology ID and its level in the spanning tree by the connection manager. Each switch may also be configured with the port number that points upstream to the connection manager of the domain either through hardware strapping or other similar mechanisms. In various embodiments, the topology ID, depth (in the tree), and upstream facing port may be configuration registers in the switch configuration space of every switch that are initialized by the connection manager during enumeration. An example format of the topology ID configuration register is shown in FIG. 9. For the illustrated example, the MSB of the topology ID may be a valid flag, which may be set to 0 on reset and set to 1 by the connection manager when the topology ID is initialized. The reserved bits of the topology ID may be set to 0.

Configuration packets flowing down the tree may be routed by the control port of a switch in accordance with one or more rules. For example, in various embodiments, the control port of the switch may be required to extract the port from the route string that corresponds to its configured level in the tree. In various embodiments, if the port is 0, the control port may be required to consume the packet. In various embodiments, if the port is non-zero, the control port may be required to forward the packet over the switch port that matches the port extracted from the route string. In various embodiments, configuration packets flowing up the spanning tree may simply be forwarded over the configured upstream facing port.

Multiple domains may interconnected in various embodiments. FIG. 10 shows example connections that may be established between multiple domains. As shown, switches 1-6 of Domain 1 may be interconnected with switches A-E of Domain 2.

In various embodiments, inter-domain links may be discovered either when the connection manager performs the initial discovery of the topology following power-on or by processing a hot-plug event. A link may be designated to be an inter-domain link when a read of the switch configuration space of the switch across the link results in an ERROR packet being sent that shows that the topology ID field has been previously assigned. When an inter-domain link is discovered, the connection manager may notify system software. The mechanism used to deliver the notification may be implementation-defined.

In various embodiments, the transport layer may only define the routing of inter-domain configuration packets between the two connection managers of the domains that are connected by an inter-domain link. Routing of configuration packets across multiple domains may be controlled by system software. When domains are daisy-chained, configuration packets passing from the originating domain may be delivered to the connection managers of every domain along the path to the target domain. The connection managers of the intermediate domains may pass the configuration packets to the system software which may be responsible for relaying the packet across the inter-domain link towards the target domain.

The routing of inter-domain REQUEST packets may be in accordance with one or more rules. For example, in various embodiments, system software on the originating domain may form REQUEST packet with a route string that points to the egress port of the domain that connects to the inter-domain link over which the packet must be forwarded and the CM bit may be set to 0. The packet may be required to be routed based on the route string at each hop within the domain and forwarded over the egress port across the inter-domain link. At the ingress port of the receiving domain, the control port may remap the route string to point to the ingress port over which the packet was received and the CM bit may be set to 1. In various embodiments, the packet may then be required to be routed to the connection manager of the receiving domain like other intra-domain configuration packets. The packet may be required to be delivered by the connection manager of the receiving domain to system software.

The routing of inter-domain RESPONSE packets may follow one or more of the same steps above. In various embodiments, system software that constructs the RESPONSE packet may use the route string in the corresponding REQUEST packet with the CM bit set to 0.

In various embodiments, the transport layer may employ a hierarchical, credit-based flow control scheme with respect to flow through the multi-protocol switching fabric to prevent or minimize overflow of receive buffers due to congestion. In various embodiments, the flow control scheme may allow a receiver to implement various buffer allocation strategies ranging from dedicated buffers per-path to shared buffer pools that are dynamically shared by multiple paths. In various embodiments, flow control may be turned off on a per-path basis. When flow control is turned off for a path, the path may be required to be provisioned with a receive buffer that can hold at least one maximum sized transport layer packet at each link.

FIG. 11 shows an example I/O complex 1106 in accordance with various embodiments. I/O complex 1106 may be similar to the I/O complex 106 of FIG. 1, including an I/O interconnect 1108 configured to couple with a device 1110. The device 1110 may be configured with one or more I/O protocols (e.g., PCI Express®, USB, DisplayPort, HDMI®, etc.).

In various embodiments, the I/O complex 1106 may be configured to connect the device 1110 with one or more protocol-specific controllers 1109 a, 1109 b, . . . 1109 n via the I/O interconnect 1108 in order to tunnel multiple I/O protocols over a common link in a manner that is transparent to the OS software stacks of tunneled I/O protocols. The protocol-specific controllers 1109 a, 1109 b, . . . 1109 n may be configured to then communicate with respective protocol-specific drivers in the OS for configuring the device 1110 as if the device 1110 was directly connected with the protocol-specific controller 1109 a, 1109 b, . . . 1109 n.

FIG. 12 shows an example hardware and software implementation of a multi-protocol apparatus (such as apparatus 100 of FIG. 1, for example) configured to tunnel multiple I/O protocols over a common link in a manner that is transparent to operating system software stacks of tunneled I/O protocols. In various embodiments, a multi-protocol apparatus may employ a multi-level hot-plug signaling scheme to support the tunneling of multiple I/O protocols over a common interconnect in a software-transparent manner.

For the implementation shown in FIG. 12, an I/O hot-plug indication may be sent by the I/O interconnect 1208 to the I/O driver in the OS (or to embedded I/O firmware) when the device 1210 is plugged into the non-protocol-specific connector port 1212 of the apparatus 1200. The hot-plug indication may then be processed by the I/O driver 1213 in the OS/firmware, resulting in communication path(s) being established between the I/O interconnect 1208 and the device 1210. In various embodiments, establishing communication path(s) may include configuring one or more paths between a source adapter and a destination adapter in a domain (described more fully elsewhere). Once the path(s) are established, mapped I/O protocol-specific configuration may be performed in which a protocol-specific hot-plug indication may be sent by the associated protocol-specific controller 1209 a, 1209 b, . . . 1209 n to the respective protocol-specific driver 1211 a, 1211 b, . . . 1211 n in the OS/firmware. The protocol-specific driver 1211 a, 1211 b, . . . 1211 n may then configure the associated protocol-specific controller 1209 a, 1209 b, . . . 1209 n as if the device 1210 was directly connected with the protocol-specific controller 1209 a, 1209 b, . . . 1209 n. At this point, the peripheral device 1210 may be visible to system software and configured to be used by applications.

In various embodiments, the apparatus 1200 may be configured such that when the device 1210 is disconnected from the port 1212, a reverse sequence of events may occur. Specifically, the protocol-specific drivers 1211 a, 1211 b, . . . 1211 n may process the protocol-specific unplug event, and then after the protocol-specific processing, the I/O driver 1213 may process the I/O unplug event.

Peripheral devices described herein (device 110, 210, 1110, or 1210, for example) may be any one of various types of devices, as noted earlier. In various embodiments, the peripheral device may be an expansion port (or other multi-protocol peripheral device) with which one or more other devices, with one or more I/O protocols, may be coupled. For example, for embodiments in which the peripheral device is an expansion port, the device may be simultaneously coupled with a PCI Express® device and a DisplayPort device, which may be coupled with an I/O complex through the expansion port device. In another example, the peripheral device may be a mobile or desktop computer system and one or more other devices may be coupled with the mobile or desktop computer system and with the I/O complex through the device. In various embodiments, multiple peripheral devices may be coupled together by daisy chaining the devices together.

In various embodiments, the peripheral device and/or the other devices coupled with the peripheral device may also include an I/O interconnect similar to one or more of the I/O interconnects 108, 208, 1108, 1208 described herein. As shown in FIG. 13, for example, a device 1310 including a multi-protocol interconnect 1301, which in turn includes a multi-protocol switching fabric 1303, may be configured to be interconnected with a multi-protocol apparatus 1300 which also includes a multi-protocol interconnect 1308 and switching fabric 1314. One or more other peripheral devices 1305 a, 1305 b, . . . 1305 n may be interconnected with the I/O interconnect 1301 via one or more corresponding non-protocol-specific ports 1312.

As noted herein, various embodiments of I/O complexes and apparatuses including I/O complexes may be configured to tunnel a multiple protocols across a multi-protocol interconnect in a software-transparent manner or substantially transparent manner. Specific examples of DisplayPort and HDMI® tunneling techniques will now be described in further detail with reference to FIGS. 14-19.

FIG. 14 shows an example architecture for mapping a DisplayPort stream over a multi-protocol switching fabric described herein. The architectural model used for mapping DisplayPort may be that of a virtual wire between the DisplayPort source and the DisplayPort sink. The DisplayPort map may behave as a DisplayPort cable replacement and may therefore be completely transparent to the DisplayPort link from a source and sink (and software stack). The DisplayPort IN adapter may terminate a DisplayPort link from a source device and encapsulate DisplayPort main link and AUZ channel transmissions inside packets and transport them across the switch network. At the other end of the network, a DisplayPort OUT adapter may decapsulate the video and AUX channel data and recreate a DisplayPort link that connects to a sink device. Hot plug detect (HPD) indications may also be transmitted as packets.

In various embodiments, when a DisplayPort link is mapped onto a multi-protocol switching fabric described herein, the continuous main link data stream may be converted into multiple types of I/O packets. FIG. 15 shows an example structure of a scan line and the packetization performed by the DisplayPort IN adapter. During the packetization, all the stuffing symbols (within a transfer unit TU of active pixel data and during the blanking periods) may be discarded by the DisplayPort IN adapter and may be recreated by the DisplayPort OUT adapter. In order to enable accurate reconstruction of the stuffing at the DisplayPort OUT adapter, the DisplayPort IN adapter may include with each I/O packet a Fill Count field that may specify the number of stuffing symbols that were discarded immediately preceding the current packet as shown.

In various embodiments, AUX channel requests may be packetized and sent as I/O packets across the multi-protocol switching fabric by the DisplayPort IN adapter and may be replayed by the DisplayPort OUT adapter at the other end. AUX channel responses may be packetized and sent as I/O packets across the multi-protocol switching fabric by the DisplayPort OUT adapter and may be replayed by the DisplayPort IN adapter at the other end.

In various embodiments, HPD indications may be packetized and sent as I/O packets across the multi-protocol switching fabric by the DisplayPort OUT adapter and may be replayed by the DisplayPort IN adapter at the other end.

DisplayPort link training may be initiated by a graphics processing unit (GPU, not illustrated) over the AUX channel and may be carried out in such a way that the DisplayPort links between the GPU and the DisplayPort IN adapter and between the DisplayPort OUT adapter and the display device get trained to the same configuration. In various embodiments, this may result in that from the GPU perspective, display device hot-plug and uplug operations may be supported in the same way for a display device connected across a multi-protocol switching fabric as for a display device attached locally to the GPU. An example link initialization sequence is shown in FIG. 16 in which training fails at the first attempt and the DisplayPort OUT adapter is forced to select a reduced bit-rate configuration.

The DisplayPort tunneling architecture described herein may support transparent tunneling of premium content streams over a multi-protocol switching fabric described herein. The multi-protocol switching fabric may appear as a DisplayPort virtual wire directly connecting a High-bandwidth Digital Content Protection (HDCP) transmitter to a HDCP receiver. The HDCP content protection mechanisms may be handled transparently by the multi-protocol switching fabric.

FIG. 17 shows an example architecture for mapping an HDMI stream over a multi-protocol switching fabric described herein. The architectural model used for tunneling HDMI may be that of a virtual wire between an HDMI source and an HDMI sink. The HDMI tunnel may behave as an HDMI cable replacement and may therefore be transparent to the HDMI source and sink (and to the software stack). As shown in FIG. 28, the HDMI IN adapter may terminate an HDMI link from a source device and encapsulate HDMI TMDS link and DDC channel transmissions inside I/O packets and transport them across the switch fabric network. At the other end of the network, an HDMI OUT adapter may decapsulate the TMDS and DDC channel data and recreate an HDMI link that connects to a sink device. HPD indications may also be transmitted as I/O packets.

In various embodiments, when an HDMI link is mapped onto a multi-protocol switching fabric described herein, the continuous TMDS link A/V stream may be converted into multiple types of I/O packets. A “video island packet” (carries pixel data) may be used to transport the active pixel data across the multi-protocol switching fabric from the HDMI IN adapter to the HDMI out adapter. Data/control island packets may be used to transport the data and control characters from the HDMI IN adapter to the HDMI OUT adapter. Example video island packet and data/control island packet formats are shown in FIGS. 18 and 19 respectively.

In various embodiments, the HDMI IN adapter may act as a proxy slave device on the bus. The HDMI IN adapter may receive the DDC transaction parameters sent by the HDMI Source and transmit them through the DDC path to the HDMI OUT adapter using a DDC request packet. The HDMI OUT Adapter may act as a proxy master device on the bus and initiate the DDC transaction to the HDMI Sink. When the HDMI Sink responds with data or acknowledgement, the HDMI OUT adapter may transmit the response to the HDMI IN adapter using a DDC response packet. When the HDMI IN adapter receives the DDC Response packet, the HDMI IN adapter may relay the transaction response to the HDMI Source.

In various embodiments, a link initialization may comprise various stages. A multi-protocol apparatus may be configured (e.g., through a software or firmware-based connection manager) to identify the active HDMI IN adapter and HDMI OUT adapter, and optionally, the plug/unplug events. A multi-protocol apparatus may be configured (e.g., through the connection manager) to set and enable paths between the HDMI IN adapter and the HDMI OUT adapter. The source may assert the 5 v signal, and the HDMI IN adapter may pass the indication to the HDMI OUT adapter, which may forward it to the sink (unless already done due to 5VO bit). The sink may respond by asserting HPD. This indication may be forwarded to the HDMI IN adapter, which may forward it to the source. In various embodiments, the HDMI IN Adapter may optionally act as a storing repeater and read the sink before asserting HPD towards the source. When the TMDS link is locked at the HDMI IN adapter, it may send a link_up indication to HDMI OUT adapter (along with the HDMI/DVI state), and TMDS LPK packets and TMU clock sync packets may be sent from this stage. The HDMI OUT adapter may generate the TMDS clock, and when stable, start driving TMDS traffic.

When premium content is streamed, the multi-protocol apparatuses tunneling HDMI may employ content protection using HDCP. The HDMI mapping architecture described herein may support transparent mapping of premium content streams over a multi-protocol switching fabric. The HDMI map may appear as an HDMI link directly connecting an HDCP transmitter to an HDCP receiver. The HDCP content protection mechanisms may be handled transparently.

FIG. 20 show an example of an overall architecture of a credit-based flow control. In various embodiments, the receiver may periodically send credit grant packets to the transmitter. The information in the credit grant packet may indicate the current unoccupied buffer space for the path. The transmitter may be allowed to send transport layer packets on a path provided the transmitter has received the sufficient number of outstanding credits from the receiver.

At each link 2034 a, 2034 b, 2034 c between the switches, the flow control may operate at multiple levels. In various embodiments, each path may be individually flow controlled. A link-level flow control may be used when dynamic buffer sharing is employed.

As shown in FIG. 21, the flow control buffer space at the receiver may be conceptually divided into two regions: a pool of buffers that are statically allocated to paths and a second pool of buffers that are dynamically shared by a set of paths. In various embodiments, the total buffer space may be flexibly partitioned between the dedicated buffers and shared buffers.

Various embodiments of the flow control architecture may allow for several buffer allocation strategies at the receiver as shown by FIG. 22. FIG. 22 shows various flow control schemes assuming eight flow controlled paths P1-P8. With static buffer partitioning, the entire buffer space may be statically divided into per-path flow control buffers. The static partitioning may be based on the expected data rate of a path. When the data rate of a path is inherently limited by the source, static buffer allocation may be used to allocate a dedicated set of buffers for the path proportional to its rate limit.

In various embodiments, the entire buffer space at the receiver may be dynamically shared by all paths that are active at the link. With dynamic buffer sharing, the receiver may advertise the entire buffer path as available buffers for every path. The link-level flow control scheme may ensure that there is no packet loss when multiple flows simultaneously burst traffic at the link. This buffer allocation strategy is useful when it is known that not all paths will simultaneously transmit at a given link.

A mix of shared buffering and static partitioning may also be employed. In various ones of these embodiments, certain paths may be allocated dedicated buffers and may not be allowed access to the shared buffer space. Other paths may not use static allocation and dynamically share the remaining buffer space.

In the remaining illustrated example of buffering allocation strategy in FIG. 22, controlled sharing of the shared buffer space may be allowed. In this scheme, each path may be restricted in the amount of the shared buffer space that it can consume. The sum total of the per-path limits for all the paths that share buffers may be greater than the total shared buffer space. The link-level flow control scheme may ensure that there is no packet loss due to oversubscription of the shared buffer space. This buffer allocation strategy may be useful to control interference between paths sharing the same buffer space at the receiver.

FIG. 23 shows an example of tracking of information at a transmitter and receiver. As shown in accordance with various embodiments of flow control. As shown, the transmitter may track, on a per-path basis, path credits consumed (PCC), which may be a count of the total number of flow control units consumed by the transport layer packet transmission on the path since the path was initialized modulo 256. The PCC may be set to 0 when the path is set up, and updated when a transport layer packet is transmitted over the path to (PCC+1) mod 256. The path credit limit (PCL) may include the most recent number of flow control units advertised by the receiver. The PCL may be set to 0 when the path is set up, and updated when a credit grant packet is received for the path by overwriting the value in the PCL with the value contained in the credit grant record for the path.

In various embodiments, in addition to the per-path flow control state, the transmitter may also track flow control information on a per-link basis. The link credits consumed (LCC) may be a count of the total number of flow control units consumed by the transport layer packet transmissions on the link since the link was initialized modulo 256. The LCC may be the sum total of all the PCC counters at the link. The LCC may be set to 0 when the port is initialized and may be updated when a credit grant packet is received for the link by overwriting the value in the link credit limit (LCL) with the value contained in the credit grant record for the link.

In various embodiments, the transmitter gating function may determine if sufficient credits have been advertised to permit the transmission of a transport layer packet at the head of the queue on a flow control enabled path. If the transmitter does not have enough credits, the transmission of packets on the path may be blocked until sufficient credits accumulate as the result of received credit grant packets. As shown, in various embodiments, the transmitter gating function test may allow a transport layer packet to be transmitted on a path only if (PCL−(PCC+1)) mod 256≦128, and if shared buffering is enabled, (LCL−(LCC+1)) mod 256≦128.

On the receiver side, the receiver may also track various information on a per-path basis. For instance, the receiver may track the path credits allocated, which may be the total number of flow control units allocated to the transmitter of the path since initialization modulo 256. The path credits allocated value may initially be set by the connection manager when the path is set up according to the buffer size and policies of the receiver. When shared buffering is enabled, path credits allocated value may be updated when additional buffer space becomes available as a transport layer packet is dequeued from the path queue to (path credits allocated+1) mod 256.

In various embodiments, the receiver may track various information on a per-link basis. For instance, the receiver may track the link credits allocated, which may contain the total number of flow control units allocated for shared buffering since initialization modulo 256. The link credits allocated may be initially set by the connection manager when the link is initialized according to the buffer size and policies of the receiver. When shared buffering is enabled, the link credits allocated value may be updated when additional buffer space becomes available as a transport layer packet is dequeued from the path queue to (link credits allocated+1) mod 256.

In various embodiments, the receiver may also track, on a per-link basis, the link credits received, which may contain the total number of flow control units received since initialization on paths using shared buffering modulo 256. The link credits received value may be set to 0 when the link is initialized, and when shared buffering is enabled, may be updated when a packet is received to (link credits received+1) mod 256.

Various embodiments may be configured to maintain a credit flow control state in sync between a transmitter and a receiver over an unreliable link. In general, plow control state tracked across a link should be maintained correctly in the presence of bit-errors. To that end, robustness mechanisms may be incorporated to protect against lost credit grant packets and data packets.

In various embodiments, each credit grant packet includes the most recent value of the credits allocated for a path and for the link. Credit grant packets may be transmitted periodically from the receiver to the transmitter. This periodic transmission of credit grant packets may provide robustness against credit grant packet loss due to bit-errors. When a credit grant packet is lost due to a bit-error, the next successfully received credit grant packet may correctly adjust the value of the credit limit counter in the transmitter.

When a data packet is lost due to a bit-error, a path-credits-allocated counter for the path may not be adjusted by the receiver. Furthermore, if shared buffering is enabled, a link-credits-allocated counter for the path may also not be adjusted. Because the transmitter has already incremented a path-credits-consumed (PCC) counter, and if applicable, a link-credits-consumed counter, the flow control may be out of sync. In order to re-establish sync and maintain robustness in the presence of lost data packets, credit sync packets may be sent periodically, by the transmitter to the receiver. The path credit sync packet may adjust the value of the path-credits-allocated counter at the receiver to compensate for the credit units consumed for the lost data packets. A link-credit-sync packet may adjust the value of the link-credits-allocated counter at the receiver to compensate for the credit units consumed for lost data packets for paths that use shared buffering.

FIG. 24 shows an example handling of the path credit sync packet at the transmitter and receiver. In various embodiments, the transmitter may insert a path credit sync packet into the data stream of each flow controlled path at some interval. For example, the transmitter may insert a path credit sync packet into the data stream of each flow controlled path every 10 seconds. In various embodiments, the path credit sync packet may not be flow controlled and therefore may be inserted at the head of the path's queue at the transmitter, as shown. The transmitter may include a snapshot of the path credit consumed counter taken at the time when the path credit sync packet was inserted at the head of the path's queue at the transmitter.

At the receiver, the receiver may insert a path credit sync packet at the tail of the path's queue when the path credit sync packet is received. When a path credit sync packet is consumed (dequeued) by the receiver, the path credits allocated counter may be update to (path credits consumed+I) mod 256, where I is the initial value of the path credits allocated counter for the path. In various embodiments, each path credit sync packet received at the receiver correctly may adjust the value of the path credits allocated counter to compensate for all data packet drops that have occurred since the previous path credit sync packet was received.

FIG. 25 shows an example handling of the link credit sync packet at the transmitter and receiver. In various embodiments, the transmitter may insert a link credit packet into the data stream of each flow controlled path at some interval. For example, the transmitter may insert a link credit packet into the data stream of each flow controlled path every 10 seconds. In various embodiments, the link credit sync packet may not be flow controlled and therefore may be inserted at ahead of all the packets of the shared buffer paths that are waiting to be transmitted, as shown. The transmitter may include a snapshot of the link credit consumed counter taken at the time when the link credit sync packet was inserted for transmission.

At the receiver, the receiver may update the link credits allocated counter to (link credits allocated+[(link credits consumed−link credits received) mod 256]) mod 256. After the link credits allocated counter is updated, the receiver may update the link credits received counter to the link credits consumed value.

In various embodiments, each link credit sync packet received at the receiver correctly may adjust the value of the link credits allocated counter to compensate for all data packet drops that have occurred on the paths using shared buffering since the previous link credit sync packet was received.

FIG. 26 is a flow diagram of an example method 2600 for configuring a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure. The method 2600 may include one or more functions, operations, or actions as is illustrated by blocks 2602-2610.

Processing for the method 2600 may start with block 2602 by identifying a plurality of switches of a switching fabric of a multi-protocol interconnect.

The method 2600 may proceed to block 2604 by creating a spanning tree representation of the plurality of switches.

The method 2600 may proceed to block 2606 by assigning unique identifications (IDs) to the switches of plurality of switches of the spanning tree. In various embodiments, the IDs may represent the relative positions of the switches within the spanning tree.

The method 2600 may proceed to block 2608 by storing the IDs and depth of the switches (in the spanning tree) in one or more registers of each of the switches.

The method 2600 may proceed to block 2610 by routing configuration packets through the spanning tree to the switches based at least in part on their respective IDs.

FIG. 27 illustrates an example method for operating a computer apparatus including a multi-protocol tunneling I/O interconnect, in accordance with various embodiments of the present disclosure. The method 2700 may include one or more functions, operations, or actions as is illustrated by blocks 2702-2722.

Processing for the method 2700 may start with block 2702 by determining whether a peripheral device has been plugged into a non-protocol-specific port of a computer apparatus including a multi-protocol tunneling I/O interconnect. Plugging may refer to a peripheral device being directly coupled with the non-protocol-specific port and/or a target peripheral device being directly coupled to some other peripheral device directly coupled with the non-protocol-specific port. In the latter embodiments, one or more other peripheral devices may be operatively disposed between the target peripheral device and the non-protocol-specific port. If no peripheral device has been plugged, then processing in block 2702 may repeat. In various embodiments, the computer apparatus may be configured to issue an interrupt signal indicating when a peripheral device has been plugged (e.g., hot-plugged).

Processing for the method 2700 may proceed to block 2704 by determining whether a data packet has been received. If no data packet has been received, then processing in block 2704 may repeat. In various embodiments, a data packet may be received from the peripheral device or from within the computer apparatus. In various embodiments, data packets within the computer apparatus may be received by the multi-protocol tunneling I/O interconnect from a protocol-specific controller (“host protocol-specific controller”) of the computer apparatus.

Processing for the method 2700 may proceed to block 2706 by determining whether the data packet was received from the peripheral device or from a host protocol-specific controller. If no data packet has been received, then processing in block 2706 may repeat.

If the data packet was received from the peripheral device, processing for the method 2700 may proceed to block 2708 by encapsulating packets of a first protocol into first transport layer packets configured to be routed through the switching fabric of the I/O interconnect. In various embodiments, packets of a second protocol, different from the first protocol, may also be encapsulated into second transport layer packets for routing through the switching fabric.

Processing for the method 2700 may proceed to block 2710 by simultaneously routing the first and second transport layer packets through the switching fabric of the I/O interconnect.

Processing for the method 2700 may proceed to block 2712 by decapsulating the transport layer packets. In various embodiments, decapsulation may be performed an adapter port of a switch of the switching fabric.

Processing for the method 2700 may proceed to block 2714 by routing the decapsulated packets to different host protocol-specific controllers of the computer apparatus.

If the data packet was received from the peripheral device, processing for the method 2700 may proceed from block 2706 to block 2716 by encapsulating packets of a first protocol into first transport layer packets configured to be routed through the switching fabric of the I/O interconnect. In various embodiments, packets of a second protocol, different from the first protocol, may also be encapsulated into second transport layer packets for routing through the switching fabric.

Processing for the method 2700 may proceed to block 2718 by simultaneously routing the first and second transport layer packets through the switching fabric of the I/O interconnect.

Processing for the method 2700 may proceed to block 2720 by decapsulating the transport layer packets. In various embodiments, decapsulation may be performed an adapter port of a switch of the switching fabric.

Processing for the method 2700 may proceed to block 2722 by routing the decapsulated packets to a peripheral device via a non-protocol-specific port of the computer apparatus.

In various embodiments, an article of manufacture may be employed to implement one or more methods as disclosed herein. FIG. 28 describes an example article of manufacture 2800. As shown, the article of manufacture 2800 may include a computer-readable non-transitory storage medium 2802 and a storage medium 2802. The storage medium 2802 may include programming instructions 2804 configured to cause an apparatus to practice some or all aspects of multi-protocol tunneling, in accordance with embodiments of the present disclosure.

The storage medium 2802 may represent a broad range of persistent storage medium known in the art, including but not limited to flash memory, optical disks or magnetic disks. The programming instructions 2804, in particular, may enable an apparatus, in response to their execution by the apparatus, to perform various operations described herein. For example, the storage medium 2802 may include programming instructions 2804 configured to cause an apparatus to practice some or all aspects of multi-protocol tunneling of the methods of FIGS. 23-27, for example, in accordance with embodiments of the present disclosure.

Although various example methods, apparatus, systems, and articles of manufacture have been described herein, the scope of coverage of the present disclosure is not limited thereto. On the contrary, the present disclosure covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents. For example, although the above discloses example systems including, among other components, software or firmware executed on hardware, it should be noted that such systems are merely illustrative and should not be considered as limiting. In particular, it is contemplated that any or all of the disclosed hardware, software, and/or firmware components could be embodied exclusively in hardware, exclusively in software, exclusively in firmware or in some combination of hardware, software, and/or firmware. 

1. A method comprising: providing, by a first port of a switching fabric of a multi-protocol interconnect to a second port of the switching fabric, a first credit grant packet and a second credit grant packet as indications of unoccupied space of a buffer associated with a path between the first port and a second port; and simultaneously routing a first data packet of a first protocol and a second data packet of a second protocol, different from the first protocol, on the path from the second port to the first port based at least in part on receipt by the second port of the first and second credit grant packets.
 2. The method of claim 1, wherein the first credit grant packet is an indication of unoccupied space of a first sub-set of the buffer, and wherein the second credit grant packet is an indication of unoccupied space of a second sub-set of the buffer.
 3. The method of claim 2, wherein the first sub-set and the second sub-set are different.
 4. The method of claim 1, wherein the providing the credit grant packet comprises determining a credit limit allocated to the path and providing the first and second credit grant packets based at least in part on the credit limit.
 5. The method of claim 1, further comprising tracking in a first counter associated with the first port a number of credit grant packets provided to the second port.
 6. The method of claim 5, further comprising periodically providing to the second port by the first port a credit sync packet indicative of remaining unoccupied space of the buffer.
 7. The method of claim 6, further comprising updating a second counter associate with the second port based at least in part on the credit sync packet.
 8. The method of claim 1, further comprising tracking in a counter associated with the second port a number of credit grant packets received by the second port.
 9. The method of claim 8, further comprising periodically receiving at the second port from the first port a credit sync packet and updating the counter based at least in part on the receiving of the credit sync packet.
 10. The method of claim 9, wherein the credit sync packet is a first credit sync packet and the counter is a first counter, and wherein the method further comprises periodically providing to the first port by the second port a second credit sync packet and updating a second counter associated with the first port based at least in part on the second credit sync packet.
 11. The method of claim 1, wherein the routing comprises routing the first and second data packets from the second port to the first port via one or more switches operatively coupled between the second port and the first port.
 12. The method of claim 1, wherein the routing comprises routing the first and second data packets from the second port directly to the first port.
 13. An article of manufacture comprising: a computer-readable non-transitory storage medium; and a plurality of programming instructions stored in the storage medium, and configured to cause an apparatus, in response to execution of the programming instructions by the apparatus, to perform a plurality of operations including: providing, by a first port of a switching fabric of a multi-protocol interconnect to a second port of the switching fabric, a first credit grant packet and a second credit grant packet as indications of unoccupied space of a buffer associated with a path between the first port and a second port; and simultaneously routing a first data packet of a first protocol and a second data packet of a second protocol, different from the first protocol, on the path from the second port to the first port based at least in part on receipt by the second port of the first and second credit grant packets.
 14. The article of manufacture of claim 13, wherein the first credit grant packet is an indication of unoccupied space of a first sub-set of the buffer, and wherein the second credit grant packet is an indication of unoccupied space of a second sub-set of the buffer.
 15. The article of manufacture of claim 13, wherein the providing the credit grant packet comprises determining a credit limit allocated to the path and providing the first and second credit grant packets based at least in part on the credit limit.
 16. The article of manufacture of claim 13, wherein the operations further include tracking in a first counter associated with the first port a number of credit grant packets provided to the second port.
 17. The article of manufacture of claim 13, wherein the operations further include tracking in a counter associated with the second port a number of credit grant packets received by the second port.
 18. A system comprising: an I/O complex including a multi-protocol interconnect having a switching fabric comprising a plurality of switches; one or more processors operatively coupled with the I/O complex; a non-transitory computer-readable storage medium operatively coupled with the one or more processors, and having stored therein a plurality of programming instructions configured to enable the system, in response to execution of the programming instructions, to: provide, by a first port of the switching fabric to a second port of the switching fabric, a first credit grant packet and a second credit grant packet as indications of unoccupied space of a buffer associated with a path between the first port and a second port; and simultaneously route a first data packet of a first protocol and a second data packet of a second protocol, different from the first protocol, on the path from the second port to the first port based at least in part on receipt by the second port of the first and second credit grant packets; a display device operatively coupled to the I/O complex and the one or more processors.
 19. The system of claim 18, wherein the system is a selected one of a desktop computer, a laptop computer, a handheld computer, a tablet computer, a netbook computer, a server, a set-top box, a digital recorder, a game console, a smart phone, a personal digital assistant, a mobile phone, a digital media player, or a digital camera.
 20. The system of claim 18, further comprising one or more antennae operatively coupled to the I/O complex by the bus and configured to establish a wireless communication link with one or more components of a wireless network.
 21. A method comprising: providing, by a first port of a first switch, a first and second credit grant packets to a second port of a second switch wherein the first and second switches are part of a multi-protocol switching fabric through which a computer can communicate with a plurality of peripheral devices, and wherein the first and second credit grant packets contain an indication of an amount of buffer space available on the first switch for data to be sent from the second switch to the first switch; and receiving, by the first port of the first switch, a first data packet of a first protocol and a second data packet of a second protocol from the second switch through a link between the first port and the second port based at least in part on receipt by the second port of the first and second credit grant packets, wherein a protocol allows a computer to communicate with a peripheral device and wherein the first protocol is different from the second protocol.
 22. The method of claim 21, wherein providing the first and the second credit grant packets in part comprises determining a credit limit allocated to a first and a second path, respectively, and providing the first and second credit grant packets based at least in part on the credit limit associated with the first and the second paths, respectively, wherein a path provides a connection between two communicating entities through the multi-protocol switching fabric.
 23. The method of claim 21, wherein the buffer space of the first switch associated with the first port is partitioned into subsets, and wherein the first credit grant packet is an indication of available space in a first sub-set of the buffer, and wherein the second credit grant packet is an indication of available space of a second sub-set of the buffer.
 24. The method of claim 21, further comprising tracking in a first counter associated with the first port a number of credit grant packets provided to the second port.
 25. The method of claim 24, further comprising periodically adjusting a value for available buffer space allocated to a path based on receiving at the first port a credit grant packet from the second port.
 26. The method of claim 21, wherein the credit grant packets are transmitted periodically.
 27. The method of claim 21, further comprising tracking in a counter associated with the second port a number of credit grant packets received by the second port.
 28. The method of claim 21, further comprising tracking, on the first switch, path credits consumed, wherein path credits consumed is an indication of the amount of buffer space consumed by data sent from the second switch to the first switch for a path.
 29. The method of claim 21, wherein the first and second protocols are PCI Express, USB, DisplayPort, or HDMI.
 30. The method of claim 21, wherein a peripheral device is a display device, a keyboard device, an expansion port, a desktop computer system, a mobile computer system, or a router.
 31. An article of manufacture comprising: a computer-readable non-transitory storage medium; and a plurality of programming instructions stored in the storage medium, and configured to cause an apparatus, in response to execution of the programming instructions by the apparatus, to perform a plurality of operations including: providing, by a first port of a first switch, a first and second credit grant packets to a second port of a second switch wherein the first and second switches are part of a multi-protocol switching fabric through which a computer can communicate with a plurality of peripheral devices, and wherein the first and second credit grant packets contain an indication of an amount of buffer space available on the first switch for data to be sent from the second switch to the first switch; and receiving, by the first port of the first switch, a first data packet of a first protocol and a second data packet of a second protocol from the second switch through a link between the first port and the second port based at least in part on receipt by the second port of the first and second credit grant packets, wherein a protocol allows a computer to communicate with a peripheral device and wherein the first protocol is different from the second protocol.
 32. The article of manufacture of claim 31, wherein the providing the first and the second credit grant packets in part comprises determining a credit limit allocated to a first and a second path, respectively, and providing the first and second credit grant packets based at least in part on the credit limit associated with the first and the second paths, respectively, wherein a path provides a connection between two communicating entities through the multi-protocol switching fabric.
 33. The article of manufacture of claim 31, wherein the buffer space of the first switch associated with the first port is partitioned into subsets, and wherein the first credit grant packet is an indication of available space in a first sub-set of the buffer, and wherein the second credit grant packet is an indication of available space of a second sub-set of the buffer.
 34. The article of manufacture of claim 31, wherein the operations further include tracking in a first counter associated with the first port a number of credit grant packets provided to the second port.
 35. The article of manufacture of claim 31, wherein the operations further include tracking in a counter associated with the second port a number of credit grant packets received by the second port.
 36. A system comprising: an input/output complex including a multi-protocol interconnect having a switching fabric comprising a plurality of switches; one or more processors operatively coupled with the input/output complex; a non-transitory computer-readable storage medium operatively coupled with the one or more processors, and having stored therein a plurality of programming instructions configured to enable the system, in response to execution of the programming instructions, to: providing, by a first port of a first switch, a first and second credit grant packets to a second port of a second switch wherein the first and second switches are part of the switching fabric through which a computer can communicate with a plurality of peripheral devices, and wherein the first and second credit grant packets contain an indication of an amount of buffer space available on the first switch for data to be sent from the second switch to the first switch; and receiving, by the first port of the first switch, a first data packet of a first protocol and a second data packet of a second protocol from the second switch through a link between the first port and the second port based at least in part on receipt by the second port of the first and second credit grant packets, wherein a protocol allows a computer to communicate with a peripheral device and wherein the first protocol is different from the second protocol; and a display device operatively coupled to the input/output complex and the one or more processors.
 37. The system of claim 36, wherein the system is a desktop computer, a laptop computer, a handheld computer, a tablet computer, a netbook computer, a server, a set-top box, a digital recorder, a game console, a smart phone, a personal digital assistant, a mobile phone, a digital media player, or a digital camera.
 38. The system of claim 36, further comprising one or more antennae operatively coupled to the input/output complex and configured to establish a wireless communication link with one or more components of a wireless network.
 39. The system of claim 36, wherein the providing the first and the second credit grant packets in part comprises determining a credit limit allocated to a first and a second path, respectively, and providing the first and second credit grant packets based at least in part on the credit limit associated with the first and the second paths, respectively, wherein a path provides a connection between two communicating entities through the multi-protocol switching fabric.
 40. The system of claim 36, wherein the buffer space of the first switch associated with the first port is partitioned into subsets, and wherein the first credit grant packet is an indication of available space in a first sub-set of the buffer, and wherein the second credit grant packet is an indication of available space of a second sub-set of the buffer. 